What we need is a "quest launcher" mod or something to make it easy just to package quests and and set their startup conditions. For example it could have the intelligence to start custom quests at beginning of game, or when player enters a certain location, or if quest not already running, or whatever people can think of.

While clearly not urgent, this would allow mixing and matching of quests at a much higher level than DFU currently deals with. For example, it could run the Perpetual Quests mod, the Reactive Factions mod, and the original DF questline and allow their disabling without the use of the console.

Not currently. DFU is hard-coded to start only _BRISIEN.txt when the game starts, and from there everything else can begin. So we can alter _BRISIEN.txt for now to add more options, but that's a rather rigid solution.

Perhaps this mod could be expanded to a "Quest Management" mod, where it would not only enable the player to execute certain quests, but to see active quests (perhaps time limits too), completed quests, failed quests, etc. You could have filters to select quests that were active in the last 30 days, 60 days, etc. Or any custom range. Quests could also be searchable not just by title but maybe text that appears during individual quest stages for easy navigation. Perhaps this could be a quality of life feature available via the logbook, which already shows active quests. The other features not available via the original logbook would need to be hidden from the start, to prevent unwanted spoilers.